Continuous disc type press



Sept. 11, 1962 A. J. A. ASPLUND CONTINUOUS DISC TYPE PRESS 2 Sheets-Sheet 1 Filed Oct. 24-, 1958 mm 2. cm 02 N9 mm ON mm on Sept. 11, 1962 A. J. A. ASPLUND commuous DISC TYPE PRESS 2 Sheets-Sheet 2 Filed Oct. 24, 1958 United States atent O 3,053,171 CONTINUOUS DISC TYPE PRESS Arne Johan Arthur Asplund, 11 Orevagen, Bromma, Sweden Filed Oct. 24, 1958, Ser. No. 769,367 Claims priority, application Sweden Oct. 28, 1957 4 Claims. (Cl. 100-158) This invention relates to a continuous disc type press for expressing liquid from wet materials such as suspensions of cellulose fibres, bark particles, peat and the like and of the kind comprising two spaced pressing discs disposed substantially co-axially on shafts having their axes disposed at a slight mutual inclination and rotating in the same direction, at least one of the discs being axially movable and being subjected to forces tending to press the discs together.

In such presses the material to be treated is fed between the discs at a point where the disc interspace is relatively large and the compressing of the material is effected by the material during the rotation of the discs being carried along to the narrowest section of the interspace, whereupon it is discharged. Usually the shafts of the discs are so inclined that the widest section of the interspace, the so-called gap, will be positioned above the shafts, whereas the narrowest section of the interspace, or the so-called nip, is disposed below said shafts.

In dewatering, for instance, a suspension of cellulose fibres in Water, the liquid expelled often contains valuable chemicals which are collected by filtration or evaporation. It is therefore of great importance that as much of the liquid as possible is expressed without being diluted. In practice the chemicals remaining with the liquid in the compressed fibrous mass can only be recovered rather uneconomically and often not at all. In dewatering a suspension of bark particles in water it is also of great value to express as much as possible of the water, since the heat value of the dried residue becomes correspondingly higher.

The absolute quantity and relative ratio of liquid expressed from the material by a disc press depends on the force pressing the discs towards one another. The comparatively large loads involved are critical for the whole structure and for the dimensions of the press. The disc press usually constitutes an integral link of a production chain where the capacity of the press is substantially determined by the preceding link. The supply of suspension of material to the disc press is thus subject to fluctuations as regards quantity and dry content, and if the expression of liquid from the material is to be maintained at a desired level, the discs of the press must be capable of moving towards and away from one another in response to said fluctuations of the material being treated.

It is known to load the discs by means of springs which due to the large forces involved must be arranged to provide a mechanical advantage of say 1:10 in order that the springs are not too heavy and bulky. While the spring force becomes improved, especially by said mechanical advantage, the interspace between the discs can only be varied to a rather inconsiderable extent. The press must be dimensioned so as to be safe with the maximum value of the spring force but this value, however, can only be used in the case of a large capacity which is not often. The degree of dewatering will there fore vary with the difierent spacings of the discs in accordance with the fluctuations of the concentration and/ or quantity of the suspension of material supplied.

The primary object of the invention is to provide a disc press wherein the force acting on the disc is independent of the spacing of the discs and hence of the capacity of the press.

Another object of the invention is to provide a disc press which is capable of reducing to a higher degree the liquid quantity of a suspension than in constructions hitherto known.

A further object of the invention is to provide a press wherein the suspension is relieved of liquid to a degree which reaches its maximum independently of the capacity of the press.

Further objects and advantages of the invention will become apparent from the following description considered in connection with the accompanying drawings, in which:

FIG. 1 is a side view partly in a longitudinal section taken along line II of FIG. 2, of a press constructed according to the invention; FIG 2 is an end view of the press shown in FIG. 1.

Referring to the drawings reference numeral 10 designates a supporting frame of a press, comprising two press discs 12, 14 rotatably mounted on said frame. Each disc has a hub portion 16 which is rigidly secured to a flange 18 of a shaft 21) by means of an annular member 22 and bolts 24. Within the frame 10 and in a bearing housing 26 attached to the frame by means of bolts 25 is located a sleeve 28 engaging the bearing housing along preferably two cylindrical surfaces 30, 32 and axially slidable in relation to said housing. The sleeve 28 is held against rotation by means of a bolt 34 entering an axially elongated aperture 36 in said sleeve. The shaft 20 is rotatably mounted in the sleeve 28 by means of two bearings 38, 40 which, together with the sleeve 28, are axially fixed relatively to the shaft 20.

The discs 12 and 14 have their shafts disposed substantially coaxially at their adjacent ends but they extend outwardly slightly inclined to one another in the vertical plane and preferably also in the horizontal plane. In the embodiment shown the opposing faces of the discs each comprises a conical frustum. Due to the slight inclination of the two shafts 20 the discs form an interspace which is wider above the shafts than below. The maximum interspace will hereinafter be referred to as the gap and the minimum interspace as the nip. When the press discs are rotating anticlockwise as viewed in FIG. 2 the gap and the nip may be positioned along a line 41, which is angularly displaced in relation to a vertical longitudinal plane through the press.

The mutually adjacent faces of the discs are provided with a filtering layer 42, such as perforated plate. On their rear faces the discs are stiffened by webs 44, and together with peripheral walls 46 and the hub portion 16 each disc defines a closed chamber 48 which communicates in the embodiment shown with a lower drain 50 through spaced peripheral openings 49. The discs have perforations 52 communicating with the chamber 48. The disc interspace is bounded inwardly by a ring member 54 of greater axial width at the top than at the bottom in accordance with the mutual inclination of the shafts 20 and with the varying size of said interspace. The ring 54 is attached to a doctor 53 in turn connected to an external ring member 55 shrouding the interspace. The doctor serves, firstly, to prevent the entering suspension from flowing over into the right half of the interspace as viewed in FIG. 2 and, secondly, to direct the dewatered material into an outlet 57 provided in the casing of the press.

The discs 12, 14 are rotated in the same direction and with the same slow speed by means of a transmission, one for each disc, such as a gear wheel 56 secured to the periphery of each disc. Each gear wheel engages a pinion 58 keyed to a drive shaft 60 mounted on the frame 10. The drive shaft 60 may be common to both transmissions provided that the pinions 58 are made slightly bevelled and helical.

According to one feature of the invention, three hydraulic devices 62, 64 and 66 are disposed below the axes of the shafts 20. Each of said devices comprises a housing 68 (FIG. 1) and a piston 70 axially slidable within said housing, said piston being subjected to liquid pressure when the press is operated. A piston rod 72 connected to the piston 70 passes through the housing and actuates a plunger 73 located in a bore 74 provided in the frame 10. The end of the plunger 73 projects from the frame and is pivotally connected to a lever 76. One end of this lever 76 is bifurcated and engages the plane cut end portion of the plunger 73. One or more part-cylindrical articulating elements 7 8 may be interposed between the plunger and the lever in order to reduce the thrust per unit area and also to permit the necessary range of movement between said parts.

The opposite bifurcated end of the lever 76 is pivotally mounted on a pivot pin 80 carried by a bracket 82 secured to the frame by means of a screw member 86. A backing roller is rotatably mounted on the central portion of the lever 76, the backing rollers being designated 88, 9t) and 92 in connection with the three hydraulic devices 62, 64 and 66, respectively. As will be seen in FIG. 1, a roller bearing is disposed between the backing roller 90 and the lever 76 and comprises an outer and an inner bearing sleeve 94 and 96, respectively, and rollers 98 interposed between the sleeves in several rows adjacent one another. The bearing is closed at both ends by means of a ring member 100 and a closure plate 102. The bearing is arranged so as to permit the backing roller to move freely axially to a limited extent relatively to the lever 76.

The external faces of the backing rollers 88, 90 and 92 are curved and preferably in such manner that the contour of said faces is part spherical. On the gear wheel 56 is secured a ring member 104 which has a circumferential roller track 106 of curved contour conforming to the transverse contour of the external roller surfaces of the backing rollers. The hydraulic devices 62, 64 and 66 are disposed radially inwardly of the backing rollers, the housings 68 of the devices being attached to a part of the frame 10 by means of bolts 108 (FIG. 2).

As seen in FIG. 2, the backing rollers are completely or practically completely uncovered externally of the frame. The backing rollers together with the levers 76 swing about the pivot pin 80 when the piston 70 undergoes axial movement. The lever 76 is dimensioned so as to cause the pressure of the backing rollers against the ring 104 and thus against the discs 12 and 14, respectively, to be equal to twice the force acting on the piston rod 72.

In operation of the press, the suspension to be treated, such as cellulose fibres in water or other liquor, is supplied at the top of the press through an inlet passage 110 shown in FIG. 2. The suspension may have a dry content of, for instance, 4-12 percent by weight and may thus vary from a strongly diluted mass to a more or less slurry-like or solid consistency. The expression suspension is thus intended to cover all proportions between the dry material and the liquid. The material to be treated follows the discs 12, 14, in their downward rotation, a progressive expression of water being effected while the distance between the discs decreases. The water expressed passes through the screen 42 and the perforations 52 to the chambers 48 and escapes from the press through the drains 50. The discs are pressed towards one another by the hydraulic devices 62, 64 and 66 while the pressure acting on the pistons is transferred to the discs through the intermediary of the levers 76 and the backing rollers 88, 90 and 82, respectively, rolling on the roller tracks 106. The treated material, thus progressively freed from water, passes the nip at the line 41 and is guided to the outlet 57 by means of the doctor 53. The dry content of the material will have increased up to, for instance 45-50% and .even higher,

While the liquid is being expressed from the material the major part of the pressure must be applied in and ahead of the nip. For this reason the backing rollers 88, and 92 are so disposed as to cause the common centre of thrust of the hydraulic pressure exerted on the discs by the rollers of the hydraulic devices to coincide with the centre of thrust of the force produced between the discs when the liquid is being expelled from the material. Since the last mentioned centre may be predetermined it is also possible to determine the desired position of the backing rollers to produce the above result. In response to any variation of the quantity of the suspension introduced per unit time or of the concentration of the suspension, the discs 12 and 14 will move toward or away from one another and this movement is rendered possible due to the provision of the cylindrical sliding surfaces 36, 32. The backing rollers 88, 90 and 92 must join in said axial movement and are so adapted due to their mounting on the pivotal levers 76. The levers then undergo a rocking movement which changes the angular position of the backing rollers relatively to the roller track 106. Due to the curved rolling faces of the backing rollers and the corresponding configuration of the roller track 106 the pressure, which is very high in itself, is distributed over the backing roller along the entire axial length thereof and this distribution is substantially maintained notwithstanding any variations of the angular position of the backing rollers. The essential feature resides in the backing rollers possessing axial mobility on their levers 76.

The hydraulic pressure acting in the devices 62, 64 and 66 is adjustable to any desired value which for a given setting remains constant independently of the axial spacing between the discs 12 and 14. This feature results in keeping the ratio of expressed liquid and content of solid substance in the discharged residue constant even if the quantity and/ or concentration of the liquid suspension supplied to the press fluctuates. Hard foreign particles passing between the press discs may pass through the nip by separating said discs without damaging them. By the above construction exceptionally high thrusts may be taken by the discs in spite of the necessary eccentricity of the pressing forces. Due to this feature the content of the solid substance in a material being treated may be increased by a considerable degree. The time required in the pressing operation to attain a predetermined dry content of the output material may be reduced which on the other hand allows the press to operate at a higher capacity, for example by a higher speed imparted to the press discs, than has hitherto been possible.

The pistons 70 in the hydraulicdevices when subjected to pressure at times when no material is passing through the press may suitably bear against the respective bases of the housings 68 of the devices, said bases then receiving the pressure acting on the pistons while the press discs 12 and 14 are relieved. The various hydraulic devices and the backing rollers cooperating therewith may be so mutually arranged as to cause the backing rollers to become operative successively in exerting the pressure when material to be treated is introduced into the press. For instance, the intermediate hydraulic device 64 may first become operative when the discs 12 and 14 start to become separatedby the incoming material. Not until after the press discs have been still further separated will the remaining servo-systems become operative either simultaneously or in succession.

One or more hydraulic devices may be adapted to cooperate with one of the press discs while the other disc bears against a thrust bearing or against springs. The opposing surfaces of the discs 12, 14 may have a plane or a curved shape. The ring member 54 may consist of a hose or similar device made of elastic material, such as rubber, and may be so dimensioned as to provide a seal for the discs at the inner edge of the interspace. The hose may follow the discs during their rotation while adapting itself by virtue of its resiliency to the spacing between the discs which varies around the circumference.

Alternatively the ring member 54 may be made self centering by being pivotally suspended to the frame, for instance by means of a preferably hollow rod. The ring member would then be movable in the central plane of the machine and up and down along the pivot rod but would be locked against rotation about the rod. The ring member 55 may be made with one half under the discs 12 and 14 movable horizontally in the centre plane of the press interspace, thus enabling the distance between the discs and this ring member to be adjusted to a value most appropriate for the operation.

While one more or less specific embodiment of the invention has been shown and described, it is to be understood that this is for purpose of illustration only and that the invention is not to be limited thereby, but its scope is to be determined by the appended claims.

.What I claim is:

1. In a press, a pair of discs between which material to be compressed is deposited, said discs being rotatively and axially movable, each disc being provided with a part formed with an annular transversely-curved track, a plurality of rollers in engagement with the track, each of said rollers having a partly-spherical face co-acting with the track, a pivoted lever on which each of the rollers is rotatively mounted, said levers permitting each roller to be pivotally moved toward or away from the disc with which it co-operates, and piston means operative to maintain the rollers against the respective tracks and permit separating movement of the discs under excess pressure.

2. In a press, a pair of discs between which material to be compressed is deposited, the discs being rotatively and axially movable, each disc being provided with a part formed with an annular transversely-curved track, a plurality of rollers in engagement with the track, each of said rollers having a partly-spherical peripheral face co-acting with the track, a pivoted lever on which each of the rollers is rotatively mounted, said levers extending in a substantially radial direction, each of said levers being pivoted at its outer end and permitting each roller to be pivotally moved toward or away from the disc with which it co-operates, each roller being axially movable on its lever, a cylinder fixedly positioned near each roller, a piston movable in each cylinder, a piston rod connected to each piston, a plunger having an end engaging the inner end of each of the levers, the inner end of each of the plungers being adjacent to and axially aligned with an end of one of the piston rods.

3. In a press, a pair of discs between which the material to be compressed is introduced, said discs being rotatively and axially movable, a plurality of rollers engaging each of the discs, each of the rollers having a partly-spherical face, a co-operating transversely-arcuate surface on each disc and against which the rollers contact, a lever on which each roller is rotatively mounted, which lever constitutes the rotative axis of the roller, one end of each lever being pivotally mounted to permit each roller to undergo a rocking movement by inclination of its lever and to be moved toward or away from the arcuate surface with which it contacts while retaining conformative contact therewith, the other end of the lever being connected to a piston rod.

4. A continuous disc-type press for expressing liquid from wet materials such as liquid suspensions of cellulose fibres, bark particles, peat or the like comprising, two substantially co-axially arranged pressing discs urged toward one another, said discs having inclined axes, means for introducing material to be dewatered between the discs in an area where the interspace between the discs is comparatively large, a tapered annulus located between the discs and around which the material to be dewatered is brought to the area of narrowest spacing between the discs for subsequent discharge, a plurality of spaced hydraulic devices for each disc, each of said devices including a piston and a cylinder, one of the same being active on the disc while the other is statio-narily maintained, a doctor arranged between the discs, said hydraulic devices being effective to permit axial movements of both of the discs so that changes in gap width between the discs due to fluctuations in the material supply will be proportioned evenly on both sides of the doctor, and a plurality of rollers connected to the hydraulic devices and operative against each disc in an area where the common pressure center co-incides with the center of thrust of the force produced between the discs during the expulsion of the liquid from the material.

References Cited in the file of this patent UNITED STATES PATENTS 241,243 Selwig May 10, 1881 2,555,733 Diserens June 5, 1951 2,793,583 Messing May 28, 1957 

